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John traveled the entire 50 km trip. If he travelled the first 20 km o

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John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 02 Mar 2018, 01:21
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[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h

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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 02 Mar 2018, 02:00
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h


If John travels 20 km at 40 km/hr he would take \(\frac{1}{2}\) hour.
The remainder of the trip - 30 km was traveled at 20 km/hr and took a time of \(\frac{30}{20} = \frac{3}{2}\) hours.

The total time taken is 2 hours and the distance traveled is 50 km.
Therefore, the average speed at which John travels is \(\frac{50}{2} = 25\)km/h (Option C)


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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 02 Mar 2018, 07:33
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MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h


Average speed = total distance/total travel time

total distance = 50 km

total travel time = time spent driving at 40 kmh + time spent driving at 20 kmh
time = distance/speed
So, time spent driving at 40 kmh = 20/40 = 1/2 hour
And time spent driving at 20 kmh = 30/20 = 3/2 hours
So, TOTAL travel time = 1/2 + 3/2 = 4/2 = 2 hours

Average speed = 50/2 = 25 kmh

Answer: C

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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 02 Mar 2018, 09:28
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h



Average Speed= Total distance traveled/Total time taken
=50/(20/40+30/20)
=50/2=25
Answer C
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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 04 Mar 2018, 19:26
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Ave Speed = ( Total Distance ) / ( Total Time )
The total distance = \(50 km\).
Total time is \(\frac{20}{40} + \frac{30}{20} = 0.5 + 1.5 = 2\)
The average speed is \(\frac{50}{2} = 25.\)
Therefore, the answer is C.

Answer : C
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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 04 Mar 2018, 19:37
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h


Average speed = total distance / total time = 50 / (20/40 + 30/20) = 50 / (1/2 + 3/2) = 25
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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 05 Mar 2018, 07:10
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h

Time for travelling first 20 Kms = 0.50 Hr
Time for travelling first 30 Kms = 1.50 Hr

Total time taken = 2.00 Hrs

So, Average speed in kmph is \(\frac{50}{2} = 25kmph\), Answer must be (C)
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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o  [#permalink]

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New post 10 Jun 2019, 19:21
MathRevolution wrote:
[GMAT math practice question]

John traveled the entire 50 km trip. If he traveled the first 20 km of the trip at a constant rate 40 km per hour and the remaining trip at a constant rate 20 km per hour, what is his average speed, in km per hour?

A. 20 km/h
B. 23 km/h
C. 25 km/h
D. 26 km/h
E. 27 km/h


We can use the equation: average = total distance/total time

50/(20/40+ 30/20)

50/(1/2 + 3/2)

50/(4/2) = 50/2 = 25

Answer: C
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Re: John traveled the entire 50 km trip. If he travelled the first 20 km o   [#permalink] 10 Jun 2019, 19:21
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